What this code means
This code may mean the SRS unit is not communicating normally with the gauge control module on the vehicle network.
What the vehicle may do
- The vehicle may show warning indicators.
- The brake system indicator behavior may help point the diagnosis.
- The code can be current or intermittent.
Possible fault areas
- Possible F-CAN wiring or connector problems.
- Possible gauge control module communication or self-diagnostic concern.
- Possible SRS unit connector, software, or unit-side concern.
- Possible dashboard harness concern.
Diagnostic path
Open on what U0155 means
On this 2010 to 2016 Honda CR-V, U0155-00 is a lost communication code with the gauge control module, diagnosed from the SRS side. In plain language, the SRS unit may not be seeing the gauge control module on the vehicle network the way it expects to. The vehicle may show warning indicators, the brake system indicator behavior may become part of the clue, and the fault area can include network wiring, connectors, gauge control module operation, SRS unit connections, SRS software status, or the dashboard harness. Because this involves the SRS system, start by finding out if the vehicle was in a collision. If it was, make sure the required parts were replaced with the correct new parts and were installed properly. Also handle the SRS safety precautions and the 12 volt battery disconnect and reconnect process before getting into connector testing.
Start with communication and indicator checks
Start with the basic system checks using the HDS. Check for F-CAN and B-CAN communication codes. If other communication codes are present, do not chase U0155 first; check what those codes mean and follow the correct path for them. If there are no other communication codes, move to the brake system indicator check. Release the parking brake, turn the vehicle to the ON mode, and watch the brake system indicator. It should come on for 2 seconds and then go off. If it does that, continue with the U0155 check. If it does not, run the gauge control module self-diagnostic function. If that check points to a gauge control module problem, pause before making a replacement call, recheck the earlier diagnostic path, and avoid guessing at the missing detail. After that path is handled, clear the code and retest. If U0155 is still present, the path then points toward the SRS unit.
Confirm the code is current
Next, clear the DTCs with the HDS. Turn the vehicle to the ON mode, wait for 10 seconds, and check for codes again with the HDS. If U0155-00 comes right back, continue to the F-CAN line check. If U0155-00 does not return, treat it as an intermittent failure and the system is OK at this time. If a different code is now present, follow the diagnostic path for that code instead.
Check the F-CAN high and low circuits for an open
For the circuit check, turn the vehicle to OFF, or LOCK mode. Disconnect the negative cable from the 12 volt battery, then wait at least 3 minutes. Disconnect SRS unit connector A, the 39P connector, and gauge control module connector A, the 32P connector. Now check continuity on both network lines: from SRS unit connector A 39P terminal No. 20 to gauge control module connector A 32P terminal No. 19, and from SRS unit connector A 39P terminal No. 21 to gauge control module connector A 32P terminal No. 20. At this point, the decision is simple: continuity is either present on the checked paths, or it is not.
Use the continuity result to choose the next move
If continuity is present, the F-CAN high and F-CAN low wires pass this open-circuit check. Then concentrate on the SRS unit side: check for a poor connection at SRS unit connector A and at the SRS unit. Before replacing an SRS unit, check the SRS unit software version with the HDS. If the software is not the latest version, update the SRS unit software and retest. If the connection is OK and the software path does not resolve it, the diagnostic path supports the SRS unit. If the code still does not clear after that, the dashboard wire harness is the remaining directed repair path. If continuity is not present, the open is in the harness between one of those two terminal pairs: SRS unit connector A terminal No. 20 to gauge control module connector A terminal No. 19, or SRS unit connector A terminal No. 21 to gauge control module connector A terminal No. 20. The repair wording on that no-continuity branch is line-broken, so pause there, recheck the test setup and the earlier path, and do not guess beyond the confirmed open harness location.
Verify the repair and close
Keep verification separate from testing. Once the directed fault is corrected, clear the DTC and retest under the same key-on conditions used to confirm the code. The takeaway is: prove the communication code is current, make sure the brake system indicator and gauge control module path are not pointing you somewhere else, then verify the F-CAN wiring between the SRS unit and the gauge control module before making a module or harness call. For more diagnostic training, visit stepdiagnostics.com.
Final check
U0155-00 is often best handled by confirming the code is current, checking for other communication faults first, then proving the network wiring path before making a module or harness decision.
For more guided automotive diagnostics, visit STEP Diagnostics.
